“For most of us the golden age of planetary exploration was the ‘70s and early ‘80s,” Hobbs said. “The time of the Apollo Moon missions—particularly those that did a lot of science—the Viking missions to Mars, and of course Voyager.”

At least four distinct plumes of water ice spew out from the south polar region of Saturn's moon Enceladus in this dramatically illuminated image, shot on Christmas Day 2009 by Cassini. Light reflected off Saturn is illuminating the surface of the moon while the Sun, almost directly behind Enceladus, is backlighting the plumes. Photo: NASA/JPL/Space Science Institute.

After that, things slowed down a lot, but in recent years there’s been something of a renaissance in the solar system.

“The first decade of the 21st Century has been as good as, if not better than, the golden age,” Hobbs believes. “Some people have called it the platinum age of planetary exploration. And if there’s a flagship of that platinum age of planetary exploration it’s got to be the Cassini-Huygens spacecraft.”

Hobbs gave a talk about Cassini, titled “Seven Years in the Saturn System,” last month at the museum. The presentation featured lots of the spectacular photography from the mission, including the discovery of seasonal colors on the second-largest planet in the solar system. Hobbs also discussed discoveries about Saturn’s rings and the intense study of the huge moon Titan. But the most fascinating part of the talk centered on the moon Enceladus, which Hobbs says has joined the astrobiologists’ short list, along with Mars and Europa, for further study.

That’s largely because of the discovery of enormous geysers at the south pole of Enceladus, which spew out ice crystals that form Saturn’s E-ring and cover Enceladus with fresh snow, making it one of the brightest objects in the solar system. The interesting thing about the E-ring is that it contains salt.

“The salt had to come from somewhere,” Hobbs explained, “so somewhere down in Enceladus there must be water in association with hot rocks. So you’ve got an energy source, you’ve got water. We don’t know yet, but maybe we have organic chemicals. If we do, this becomes one of the likeliest places we could find life in the solar system.

“Enceladus has rapidly become one of the most important bodies for us to study,” he added.

Cassini’s work in the Saturn system is planned to continue until the summer of 2017, when it will make a handful of spectacular proximal orbits very close to Saturn’s cloud tops before it runs out of fuel and is crashed into the ringed planet.

That’s presuming Cassini keeps working. Hobbs notes that while the warranty has long since expired, the school bus-sized craft hasn’t missed a beat since it was launched in 1997.

“Space is a harsh environment, particularly when you go a billion miles from the Sun,” Hobbs noted. “It gets cold out there, and every time you go into the shadow of Saturn or one of the moons, it drops dramatically. So given our experience with technical things, it is kind of a surprise” that Cassini is still functioning, he said. “On the other hand, we in America seem to be building some really good stuff these days.”

It will be fascinating to see what wonders Cassini finds before the mission ends five years from September.